The current research program was designed to further our knowledge about the nature of schizophrenia by a prospective, longitudinal, investigation of the following questions about schizophrenic cognition: 1) What are the essential or primary features which are always present in schizophrenic thought disorders? Do specific types of thought pathology differentiate patients into "true" schizophrenics and reactive psychoses? 2) What is the longitudinal course of schizophrenic thought disorders? Are thought disorders primary symptoms which persist when the patient is in the recovery stage? 3) What factors influence or lead to schizophrenic thought pathology? 4) What is the nature, extent, and persistence of psychotic symptoms and first rank symptoms in schizophrenia? The research involves a multifaceted longitudinal investigation of thought disorders and psychotic symptoms, using a battery of structured interviews, performance tests, cognitive measures, personality inventories and behavioral ratings. These are being used to assess psychotic symptoms, bizarre-idiosyncratic thinking, associative thinking, overinclusion, concrete thinking, logical thinking, boundary disturbances, egocentrism, primary process drive dominated thinking, and other aspects of cognition. Two samples of schizophrenic and nonschizophrenic patients are being assessed at five time periods, lasting up to 11 years for one subsample. Patients are evaluated at the acute phase, during partial recovery, and followed up at various phases during the posthospital period, for disordered thinking and psychotic symptoms. They are also assessed for affective symptoms, rehospitalization, personality variables, and social and work adjustment. The data are used to evaluate a number of theories about prognostic factors, disordered cognition, and psychosis, and to assess the long-term clinical course and level adjustment in modern day schizophrenia.